package com.data.basic.chapter12;

import java.util.ArrayList;
import java.util.Random;

/**
 * 平衡二叉树：左边的都比上面小，右边都比上面大  自平衡的树
 * @param <K>
 * @param <V>
 */

public class AVLTree<K extends Comparable<K>, V> {

    private class Node{
        public K key;
        public V value;
        public Node left, right;
        public int height;//节点的高度，用于计算平衡因子

        public Node(K key, V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;// 高度默认为1  叶子节点默认为1
        }
    }

    private Node root;
    private int size;

    public AVLTree(){
        root = null;
        size = 0;
    }

    public int getSize(){
        return size;
    }

    public boolean isEmpty(){
        return size == 0;
    }
    //判断该二叉树是否是一颗二叉搜索树
    //利用二分搜索树的性质    中序遍历是按照顺序的
    public boolean isBST(){
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root,keys);
        for (int i=1;i<keys.size();i++){
            if (keys.get(i-1).compareTo(keys.get(i))>0){
                return false;
            }
        }
        return true;

    }

    /**
     * 对节点y进行向右旋转，返回旋转后新的节点x
             y                                    x
            / \                                 /   \
           x   T4         向右旋转（y）         z     y
          / \             -------------->     / \   / \
         z   T3                              T1 T2 T3 T4
        / \
       T1  T2

     原因：y节点的条件 ===>  balanceFactor>1&&getBalanceFactor(node.left)>=0
     操作：
     x.right = y
     y.left = T3
     */
    private Node rightRotate(Node y){
        Node x = y.left;
        Node T3 = x.right;
        //右旋
        x.right = y;
        y.left = T3;

        //更新height值
        y.height = Math.max(getHeight(y.left),getHeight(y.right))+1;
        x.height = Math.max(getHeight(x.right),getHeight(x.left))+1;

        return x;
    }
    /**
     * 对节点y进行向右旋转，返回旋转后新的节点x
             y                                    x
            / \                                 /   \
           T1  x         向右旋转（y）         y     z
              / \         -------------->    / \   / \
             T2  z                          T1 T2 T3 T4
                / \
               T3  T4

     原因：y节点的条件 ===>  balanceFactor>1&&getBalanceFactor(node.left)>=0
     操作：
     x.left = y
     y.right = T3
     */
    private Node leftRotate(Node y){
        Node x = y.right;
        Node T1 = x.left;
        //右旋
        x.left = y;
        y.right = T1;

        //更新height值
        y.height = Math.max(getHeight(y.left),getHeight(y.right))+1;
        x.height = Math.max(getHeight(x.right),getHeight(x.left))+1;

        return x;
    }

    /**
     * 向以node为根的二分搜索树中插入元素(key, value)，递归算法
     * 返 回插入新节点后二分搜索树的根
     *
     * @param node
     * @param key
     * @param value
     * @return
     */

    private Node add(Node node, K key, V value){

        if(node == null){
            size ++;
            return new Node(key, value);
        }

        if(key.compareTo(node.key) < 0)
            node.left = add(node.left, key, value);
        else if(key.compareTo(node.key) > 0)
            node.right = add(node.right, key, value);
        else // key.compareTo(node.key) == 0
            node.value = value;

        // 更新height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(node);
        if(Math.abs(balanceFactor) > 1)//todo
            System.out.println("unbalanced : " + balanceFactor);

        /**平衡维护  LL  此种情况是: 需要右旋
         *  本节点node的平衡因子大于1，所以两边的高度差等于2，所以两边有一个高度是h，另一个高度是h+2
         *  如果左子树的平衡因子大于0，也就是等于1，就是说node.left的左子树比右子树高1个单位，所以可以确定形状了。
         */
        if(balanceFactor>1&&getBalanceFactor(node.left)>=0){
            return  rightRotate(node);
        }
        /**平衡维护 RR   此种情况是: 需要左旋*/
        if(balanceFactor<-1&&getBalanceFactor(node.left)<=0){
            return  rightRotate(node);
        }
        /**平衡维护  LR  此种情况是: 需要左旋成LL*/
        if (balanceFactor>1&&getBalanceFactor(node.left)<0){
            node.left =  leftRotate(node.left);
            return rightRotate(node);
        }

        /**平衡维护  RL  此种情况是: 需要右旋变成RR 再左旋*/
        if (balanceFactor<-1&&getBalanceFactor(node.right)>0){
            node.right = rightRotate(node.right);
            return leftRotate(node);

        }

        return node;
    }

    //中序遍历
    private void inOrder(Node node, ArrayList<K> keys) {
        if (node==null){
            return;
        }

        inOrder(node.left,keys);
        keys.add(node.key);
        inOrder(node.right,keys);
    }

    //判断该二叉树是否是一个平衡二叉树
    public boolean isBalanced(){
        return isBalanced(root);
    }


//是否是平衡的
    private boolean isBalanced(Node node) {
        if (node==null){
            return true;
        }
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor)>1){
            return false;
        }
        return isBalanced(node.left)&&isBalanced(node.right);
    }

    // 获得节点node的高度
    private int getHeight(Node node){
        if(node == null)
            return 0;
        return node.height;
    }

    /**
     *获得节点node的平衡因子    左子树高度-右子树的高度
     */
    private int getBalanceFactor(Node node){
        if(node == null)
            return 0;
        return getHeight(node.left) - getHeight(node.right);
    }

    // 向二分搜索树中添加新的元素(key, value)
    public void add(K key, V value){
        root = add(root, key, value);
    }

    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key){

        if(node == null)
            return null;

        if(key.equals(node.key))
            return node;
        else if(key.compareTo(node.key) < 0)
            return getNode(node.left, key);
        else // if(key.compareTo(node.key) > 0)
            return getNode(node.right, key);
    }

    public boolean contains(K key){
        return getNode(root, key) != null;
    }

    public V get(K key){

        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue){
        Node node = getNode(root, key);
        if(node == null)
            throw new IllegalArgumentException(key + " doesn't exist!");

        node.value = newValue;
    }

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node){
        if(node.left == null)
            return node;
        return minimum(node.left);
    }

    // 删除掉以node为根的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node){

        if(node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size --;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }

    // 从二分搜索树中删除键为key的节点
    public V remove(K key){

        Node node = getNode(root, key);
        if(node != null){
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    /**
     *
     * @param node  要删除元素的根节点
     * @param key
     * @return
     */
    private Node remove(Node node, K key){

        if( node == null )
            return null;

        Node retNode = null;//保存返回的node

        if( key.compareTo(node.key) < 0 ){
            node.left = remove(node.left , key);
            retNode = node;
        }
        else if(key.compareTo(node.key) > 0 ){
            node.right = remove(node.right, key);
            retNode = node;
        }
        else{   // key.compareTo(node.key) == 0

            // 待删除节点左子树为空的情况
            if(node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size --;
                retNode = rightNode;
            }

            // 待删除节点右子树为空的情况
            if(node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size --;
                retNode = leftNode;
            }
            if (node.right!=null&&node.left!=null){
                // 待删除节点左右子树均不为空的情况

                // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
                // 用这个节点顶替待删除节点的位置
                Node successor = minimum(node.right);
                //删除最小值
                successor.right = remove(node.right,successor.key);
                successor.left = node.left;

                node.left = node.right = null;
                retNode = successor;
            }
        }

        if (retNode==null){//删除只有根节点的情况
            return null;
        }
        //更新改动后节点的height
        retNode.height = 1+ Math.max(getHeight(retNode.left),getHeight(retNode.right));
        //计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);


        //平衡维护  LL
        if (balanceFactor>1&&getBalanceFactor(retNode.left)>=0){
            return rightRotate(retNode);
        }
        //平衡维护  RR
        if (balanceFactor<-1&&getBalanceFactor(retNode.right)<=0){
            return leftRotate(retNode);
        }
        //平衡维护 LR
        if (balanceFactor>1&&getBalanceFactor(retNode.right)<0){

            retNode.right = leftRotate(retNode.right);
            return rightRotate(retNode);
        }
        //平衡维护 RL
        if (balanceFactor<-1&&getBalanceFactor(retNode.left)>0){
            retNode.left = rightRotate(retNode.left);
            return leftRotate(retNode);
        }
        //没有影响平衡的状态
        return retNode;


    }

    public static void main(String[] args){

        System.out.println("Pride and Prejudice");
        Random random = new Random();
        AVLTree avlTree = new AVLTree();
        for (int i=1;i<1000;i++){
            avlTree.add(i,random.nextInt(i));
        }

//        ArrayList<String> words = new ArrayList<String>();
//        if(FileOperation.readFile("pride-and-prejudice.txt", words)) {
//            System.out.println("Total words: " + words.size());
//
//            AVLTree<String, Integer> map = new AVLTree<String, Integer>();
//            for (String word : words) {
//                if (map.contains(word))
//                    map.set(word, map.get(word) + 1);
//                else
//                    map.add(word, 1);
//            }
//
//            System.out.println("Total different words: " + map.getSize());
//            System.out.println("Frequency of PRIDE: " + map.get("pride"));
//            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));
//        }

        System.out.println();
    }
}